Filter elements



'Dec.2,1958 E. A. STOKES 2,862,624

FILTER ELEMENTS Filed April 26, 1955 ABCDaE C D E F U U P [)0 N DOWN 00 UP UP DOWN I 7 I K7 Y Ed 2.

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United StatesPatent 2,862,624 FILTER ELEMENTS Edward Arthur Stokes, Guildford, England, assignor to Vokes Limited, Guildford, England Application April 26, 1955, Serial No. 503,953

- 2 Claims. or. 210-493 such as paper or compressed fibre, which have little inherent rigidity it is often necessary to support the fins by means of wire gauze or by a grid or the like in order to prevent the side walls of adjacent fins from contacting one another and becoming ineffective as they are distended by the pressure of the fluid being filtered. In the case of expendable elements it is not uncommon for the cost of the element supporting medium or structure to exceed by far the cost of the filtering medium itself.

It is the object of the present invention to provide an element of the finned or pleated type, which requires little or no support except at the periphery, but which is capable of maintaining the walls of each fin or pleat in proper spaced relationship under ordinary conditions of use.

According to the invention a finned or pleated filter element is provided with series of corrugations or zig-zag folds substantially normal to the ordinary lines of fold of the fins or pleats, the ordinary lines of fold of the fins or pleats being modified from straight lines to appropriate zig-zag lines so that the apices of the fins or pleats are maintained apart while the walls of the fins or pleats are stiffened by the corrugated or zig-zag folded form thereof.

Put in another way a filter element according to the invention is comprised by at least one sheet of filtering medium formed with pleats or fins by folding the sheet in alternately directed bends in zig-zag fashion, the folded sheet being then folded inv similar zig-zag fashion substantially at right angles to the first lines of fold, the said first lines of fold being then modified from parallel straight lines to parallel zig-zag lines, whereby the fins or pleats are strengthened by folds transverse to their depth and maintained open by the geometrical form of those folds.

The resultant shape is not easy to visualise, but an illustrative model can be easily made in the following manner. Take a rectangular sheet of paper and fold it in half with a light fold parallel to one edge. Now fold the double sheet in zig-zag fashion at right angles to the first fold to form a number of pleats or corrugations. Pull the free edge of the apex of each corrugated half sheet away from its complementary edge by a short distance (say A"), and, maintaining this relationship, impress theresultant modification of fold firmly onto the first made lightfold. This fold will now be found to be modified from a straight line to a zig-zag line, and if the folded sheet is extended concertina-fashion along an axis parallel to the original light fold it will be found that the corrugated free edges are maintained effectively apart. The original light fold is representative of one of the fin edges of an element and the folds at right angles thereto are representative of the stiflt'ening corrugations.

The invention is illustrated in the accompanying drawings of a filter element section and a blank from which it may be folded. In the drawings:

Fig. 1 is a perspective view of a part of an element. Fig. 2 is a plan of a blank from which a part of an element such as shown in Fig. v1 can be folded.

Considering first Fig. l and assuming the right hand side of the drawing to represent the fluid inlet side it will be seen that the element presents to the flow folded edges 2,4, 6 and 8 and a plain edge 10, while the exit side of the element presents a plain edge l'and folded edges 3, 5, 7 and 9. There are, in effect four complete pleats. All of the pleats are formed substantially at right angles to their folds with a zig-zag or corrugated forma-' tion by the impression therein offolds having apices or lines of fold A, B, C, D, E, F, G, H and J.' These folds not only add strength to the pleated element but keep the pleats apart owing to their geometry. Fig. 2 shows Likewise the lines A, B I represent the lines ofzig-zag folding A, B J in Fig. 1.

The fold lines on Fig. 2 are designated Up or Down as the case may be to indicate that the adjacent surfaces are bent upwards or downwards.

Bending the sheet of Fig. 2 in the senses indicated will produce the element of Fig. 1.

The depth and pitch of the corrugations running across the length of the fins can be varied, depending upon the initial rigidity of the filter medium employed; for lower rigidity of filter medium the depth and pitch of the corrugations is reduced to obtain the required stilfness.

It may not generally be possible to fold the full number of fins required to form the filter element in one operation, due to the fact that when applying the corrugations cracking of the filter medium may occur when a number of layers are corrugated in the same operation. Under such circumstances, single sheets or three or four fins, dependent upon the nature of the filter medium, can be corrugated at a time, and having impressed the crease lines, the material may then be opened out. Having corrugated sufiicient sheets or sections to form the complete filter element, the leading and/or trailing edges of adjacent sections are then glued together in jigged relationship by .an adhesive. The edges of the sheets or sections may be coated with a pressure adhesive substance to facilitate this operation. Having performed the sticking operation the element can then readily be closed in on the width and the corrugations throughout the length of the fin will again take shape.

A variety of methods of sealing the filter element into its final housing may be devised, but the cheapest method is to use adhesive to stick the sides of the fins to the walls of the filter housing. Alternatively the Walls of the filter housing may be constructed to have adjacent to them the required number of tapered fingers attached only at one edge of the filter housing. The paper element can then be inserted into the housing in such a way that a tapered finger is situated between each corrugated tin of the element, thus retaining the folded edges of the fins in close contact with the wall of the housing. Dependent upon the rigidity of the medium used it may or may not be necessary to support the fins along the leading and trailing edges at intervals across the width of the element.

little way into the depth of the cavity between the fins, I

can be employed.

I claim:

1. A filter element comprised by a sheet of permeable" filter material, said' sheet being folded in zigzag fashion along one series of parallel straight lines and being folded in zigzag fashion along. another series of alternately inclined straight lines substantially but not precisely at right angles to the said first series of lines, the aberration" from rectangularity being such as to maintain pleats formed by said first folding apart from one another at minor acute angles.

2'. The method of forming a'pleated filter element, comprising folding at least one sheet of filtering medium upon itself in alternately directed folds in zigzag fashion along a first series of straight parallel lines to form first pleats, folding the pleated sheet upon itself in similar zigzag fashion along a second series of straight parallel lines substantially at right angles to said first series of lines to form a plurality of second pleats in each of said first pleats with the secondpleats in interleaved relation,

expanding the folded sheet to dispose said first pleats at minor acute angles relative to each other, and modifying the folds coincident With said first series of straight parallel lines to extend along alternately inclined straight lines generally but not precisely at right angles to said second series of lines, whereby the first pleats are strengthened by folds transverse their depth and main tained Open at minor acute angles by the geometrical form of those folds.

References Cited in the file of this patent UNITED STATES PATENTS 

